1. Field of the Invention
The present invention relates to a method, system, and program for an adaptor to read and write to system memory.
2. Description of the Related Art
In certain computing environments, multiple host systems may communicate with one or more control units, such as an IBM Enterprise Storage Server (ESS)®, for data in a storage device managed by the ESS receiving the request. The control unit manages access to storage devices, such as interconnected hard disk drives through one or more logical paths. (IBM and ESS are registered trademarks of IBM). The interconnected drives may be configured as a Direct Access Storage Device (DASD), Redundant Array of Independent Disks (RAID), Just a Bunch of Disks (JBOD), etc. The control unit includes a host adaptor to receive I/O requests from the host. In certain systems, the host may read and write blocks of data having a certain format, such as 512 byte blocks and the control unit may store data in a different format by adding metadata to the blocks from the host, resulting in 524 bytes per block.
In one system, the host adaptor may transfer blocks to write to logical block addresses to a memory controller for a cache. The memory controller may then handle the virtual address mapping of the logical blocks to write to the physical pages in the cache. When requesting data, the host adaptor may provide the memory controller the logical blocks to read and the memory controller may translate the requested logical blocks to physical pages in the cache. The memory controller then fetches the data from the determined physical pages to return to the host adaptor to, in turn, return to the host.